Medical irrigation syringes, for example, are often employed for irrigating wounds during surgery, flushing and draining body cavities, and for many other medical purposes.
One type of irrigation syringe is of the bulb-type which includes a syringe barrel and a resilient compressible bulb connected to the syringe and which is squeezed to effect a positive pressure and released to provide a negative pressure within the syringe barrel. The bulb may be formed of a suitable elastomer or plastic and may be either integrally formed with the barrel or formed as a separate member connected to the barrel.
There have been several problems associated with bulb-type syringes. For example, where the bulb and barrel are formed as an integral single-piece unit, the plastic forming the bulg is generally determined by the type of plastic required for the barrel. While such single-piece syringes are economical and useful under many conditions, control of bulb compression and the control of fluid flow is generally not as good as it is with syringes of the type having separate bulb and barrel members. This is because the bulb, when made separately from the barrel, can be formed of a material which is more elastic than that of the barrel and, in general, can provide better compression control. Also, with single-piece syringes, the integral barrel cannot be removed from the bulb so that the barrel cannot be used as a funnel, as is often desired.
Syringes of the type having separately formed bulb and barrel members usually include a bulb having a compressivle bulbous portion connected to a generally cylindrical connector end portion which end portion is connected with the barrel by a tight frictional fit but is usually made to be manually separable from the barrel so that the barrel can be used alone as a funnel. Also, where the bulb and barrel are separable, they are more readily cleaned. However, in some constructions, depending upon the manner in which the bulbous portion is compressed, a fluid leak between the barrel chamber and the atmosphere may occur. This is more apt to happen when the bulb is compressed by squeezing opposed sidewalls of bulb between the thumb and fingers as opposed to when the thumb is used to move the center of the proximal end of the bulb distally. Squeezing the opposed sidewalls tend to pull portions of the connector portion of the bulb radially inwardly away from the barrel wall and tends to cause such a leak. In order to reduce the chance of fluid leaks during compression of the bulb, relatively rigid inserts have been placed in the connector portion of the bulb so that when the bulb is compressed, the relatively rigid supporting insert tends to prevent leakage. Such inserts increase the number of parts, assembly time and cost of the product.
Irrigation syringes of the type that employ a slidable plunger having a piston at the distal end may be employed where positive and negative pressures greater than those obtainable with the bulb-type syringe are required. Syringes of the bulb-type as well as of the piston-type are employed in the medical field for various applications.